1. Field of the Invention
The invention concerns a high current coaxial connection of the type formed by two plug elements that can be connected with one another, in particular for connection of a current-carrying coaxial line to a gradient coil of a magnetic resonance apparatus, as well as a gradient coil with a connected high current coaxial line.
2. Description of the Prior Art
In addition to other apparatuses, magnetic resonance apparatuses (for example) in which the examination subject is exposed to a strong magnetic field for generation of image exposures are known from medical technology. This leads to an alignment of the nuclear spins of the atoms located in the magnetic field, and the measurement signal for the imaging is obtained by the excitation of oscillations by radio-frequency energy. In order to produce a spatial coding of the signals, magnetic gradient fields are used that are generated along the three spatial directions using coils known as gradient coils. The coils for the individual spatial directions are combined into a gradient coil system that, under the circumstances, include a number of individual coils associated with the three spatial directions and is often also designated as a “gradient coil” for short. This gradient coil is spatially fixed in a sealing compound in which it is cast.
A high current must be supplied to the gradient coil for generation of the gradient fields. The currents employed lie at a few 100 A. For instance, 500-900 A is a typical value.
Presently it is frequently the case that, since no suitable high current coaxial connections are available for connection of such a gradient coil, the coaxial lines must be split into two individual conductors before the connection to the coil, with the individual conductors in turn being screwed down at the coil. The high current that must be fed to the gradient coil thus no longer flows coaxially. This leads to high alternating forces in the scatter field of the magnet due to the individual conductors, and thus to a high dynamic material load. This presents the danger of a breakage or a loosening of the contact, and burning or carbonizing can arise due to the high energy at the general purpose amplifier (GPA).
To address this problem, attempts have already been made to make the connection of the gradient coil by means of a high current coaxial connection that includes a plug and a counter-plug that can be detachably connected therewith, the plug exhibiting a contact bolt (housed in an insulation bushing) that can be axially displaced in a direction counter to a reset force. The insulation bushing is housed in a contact bushing that is overlapped by a coupling mounting, while the counter-plug includes a central counter-contact bolt that is held in an insulation bushing that is in turn housed in a counter-contact bushing that interacts with the coupling mounting for connection of the plug with the counter plug. Upon connection of the plug with the counter-plug, the contact bushing as well as the insulation bushing are then moved relative to a contact bolt abutting the counter-contact bolt to establish a reset force, and the contact bushing is moved against the counter-contact bushing. The reset force for such a high current coaxial connection can be generated, for example, by a spring element or a spring element contact.
However, the contact surfaces via which the electrical contact is established lie transverse or perpendicular to the axis of the plug connection, such that a relatively rigid mounting is required to ensure a permanent electrical connection (in particular with regard to forces that act in the axial direction).